1. Field
This relates generally to ocular laser treatments and, more specifically, to optimization of photothermal therapy of the eye.
2. Related Art
Every year, thousands of patients in the United States and other countries undergo laser-based interventional treatments of the eye. Such treatments typically involve the application of laser energy in the form of a laser treatment beam having a controlled power and controlled duration to targeted tissue structures to create visible or sub-visible lesions. These treatments may be used to address clinical problems, such as diabetic retinopathy, diabetic macular edema, neovascular disease, age-related macular degeneration, glaucoma, retinal vascular leakage resulting from angiogenic factors produced in response to retinal inflammation and ischemia, or the like.
One conventional laser-based treatment that may be used to treat the eye is retinal photocoagulation, which may typically be performed with a 514 or 532 nm laser using exposure durations from 50 to 200 ms and spot sizes ranging from 100 to 500 μm. Early retinal photocoagulation techniques included the application of relatively intense retinal lesions, resulting in thermal damage that undesirably extended into the inner retina. More recent retinal photocoagulation techniques include the application of moderate lesions to limit damage to the ganglion cell layer and nerve fiber layer of the eye. Even more recently, a retinal photocoagulation technique has been developed that includes the application of patterns of multiple spots onto the eye using a scanning laser. These applications of patterned spots can be applied with shorter pulse durations in the range of 10-30 ms. Since heat diffusion is decreased due to shorter exposure time, these lesions tend to be lighter and smaller than their single-point counterparts.
Using any one of the laser treatment techniques described above, physicians may treat a patient's eye using multiple laser treatment beam applications to form multiple lesions over a desired portion of the eye. For example, physicians currently apply a single application of the laser treatment beam to patient's eye and observe the resulting lesion. The physician may then apply another application of the laser treatment beam at a location near the previously generated lesion. Typically, the location of the subsequent laser treatment beam application is determined by the physician and the distance between successive laser treatment beam applications corresponds to a certain fraction of the lesion diameter. In this way, the physician may generate a pattern of multiple lesions over a desired treatment area of the patient's eye.
While this technique may be used to effectively treat a patient using a single-spot laser treatment beam that generates visible lesions, it may not be used to treat a patient using a laser treatment beam that generates sub-visible lesions, as the physician would be unable to position the laser treatment beam based on a previously formed sub-visible lesion. Moreover, this technique may not be used to treat a patient using a patterned laser treatment beam since the pattern should be determined prior to the application of the patterned laser treatment beam.